The night was sad. The center failed to hold. Did I blame the rioting kids? I did. Did I blame Trump? I did. This, Mr. Trump, I thought, is why we practice civility. This is why, before we say exactly what is on our minds, we run it past ourselves, to see if it makes sense, is true, is fair, has a flavor of kindness, and won’t hurt someone or make someone’s difficult life more difficult. Because there are, among us, in every political camp, limited, angry, violent, and/or damaged people, waiting for any excuse to throw off the tethers of restraint and get after it. After which it falls to the rest of us, right and left, to clean up the mess.